West Nile virus positive mosquitoes detected in Las Vegas

By Dr. Ananya Mandal, MDJun 7 2017

According to the health officials in Southern Nevada, mosquito samples from multiple Las Vegas neighbourhoods have tested positive for the West Nile virus. The affected zip code areas according to the officials are 89011, 89110 and 89146. These areas were being combed for Zika virus in mosquitoes. One such case of human West Nile virus infection has been confirmed in Clark County a few weeks ago.

Image Credit: By Leena Robinson / Shutterstock

West Nile virus is a virus that is carried by infected birds. It is spread by infected mosquitoes. It leads to fever in mild cases but may lead to more life threatening consequences such as inflammation of the brain or encephalitis or meningitis that is caused due to inflammation of the linings of the brain and the spinal cord. After the bite from the infected mosquito, the infection manifests anytime between 2 and 14 days. This period of incubation maybe longer in persons with a compromised immunity.

In nearly 70-80% individuals infected with this virus there may be no symptoms at all. Around 1 in 5 persons with the infection may develop fever and other symptoms including joint pains, vomiting, diarrhea, or rash, headaches and body ache. Recovery from the infection is complete but a weakness after the infection may last for a few weeks and even for a few months.

Rarely in 1 in 100 infected individuals, there may be complications. This includes encephalitis or meningitis. These individuals may present with symptoms such as intense headaches, high non-relenting fever, stiff necks, coma, tremors, convulsions or seizures and paralysis of one or more limbs. Around 10% of persons with these complications may succumb to the infection. Sometimes the residuals neurological problems after recovery in these severe cases may persist for weeks, months, years or even lifelong.

The transmission of this virus has been reported in Middle East, Africa, Europe, parts of Asia including India and Australia. It was first found in North America in 1999 and since then has been spreading to United States and Canada.

The infection affects humans by the bite of an infected mosquito that has fed on infected birds. Other animals too can be affected. It may also spread in rare cases, via blood transfusions, organ transplants. Spread from mother to the fetus or baby is possible during pregnancy, delivery or breastfeeding.

Persons living in areas where the West Nile virus is present in mosquitoes are at risk of getting this infection. Outbreaks of this viral infection are seen almost every summer since its first detection in 1999 said officials. Persons working outdoors are more at risk of getting mosquito bites and are thus more at risk of this infection.

At present there are no vaccines against this viral infection. Thus prevention of mosquito bite is the only way to prevent this infection. At present there are no medications to treat West Nile virus infection. Pain and fever may be relieved with over-the counter medications. Hospitalizations are needed in severe cases.